create_payment_link

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations (readOnlyHint=false, openWorldHint=true), the description reveals crucial behaviors: 'Nothing is charged until the buyer completes payment there,' env='test' charges nobody, uniqueness requirements for reference_id, refusal of unsigned webhooks, and the fact that `code` and `webhook_secret` are not retrievable later. It also notes the call is never retried and has no idempotency key, providing comprehensive operational transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise yet information-dense, with each sentence serving a distinct purpose: purpose, alternative, charge behavior, reference_id uniqueness, webhook constraint, data irrecoverability, and idempotency warning. It is front-loaded with the primary action and avoids redundant phrasing.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (9 parameters, output schema, annotations), the description covers all critical operational aspects: return value semantics, environmental differences, webhook security pairing, uniqueness constraints, data persistence caveats, and retry behavior. It leaves no major gaps that would cause an agent to misuse the tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description adds significant value by explaining parameter interdependencies (e.g., 'Passing `webhook_url` without `webhook_secret` is refused'), uniqueness requirements, and the ambiguity in line_items reconciliation. It also clarifies the meaning of env values and the irrecoverability of `code` and `webhook_secret`, enriching the schema's bare definitions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with 'Create a Wayl payment link and return the checkout URL to send the buyer,' a specific verb+resource statement that clearly distinguishes this from siblings like `sell_book` and `get_payment_link`. It further clarifies that this is the 'general-purpose builder,' reinforcing its role.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly contrasts with the sibling tool: 'For selling a book, `sell_book` is usually less work — it derives the line items and reference ID for you.' It also explains when to poll `check_order_paid` and warns about the env distinction, giving clear context for when to use this tool vs alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.